The subject invention relates to a battery plate feeder and in particular to a plate feeder which picks plates serially off of a vertical stack of plates which is moved upwardly toward the pick-up head each time a plate is removed from the stack.
Plates for storage batteries are serially fed to another machine which inserts them into microporous pouches for insertion into battery cases. Mechanical plate feeders are used to remove plates from a stack of plates and feed them to the other machine. The prior art battery plate feeders continuously urge a horizontal stack of plates against a rotating cylindrical pick-up head having multiple pick-up units located about its periphery. Vacuum is introduced in each pick-up unit as it reaches the stack of plates to cause the forwardmost plate in the stack to become affixed to the pick-up unit, and the vacuum is discontinued when the plate reaches an outfeed conveyer which carries the plate to the sealing machine.
In order to keep the plate being removed from striking the next plate in the stack, and thus either dislodging the plate from the pick-up unit or displacing the next plate in the stack, a gap must be created between the forwardmost plate in the stack and the pick-up head. The vacuum then pulls the forwardmost plate across this gap into contact with the pick-up unit. Since the plates are being continuously urged toward the pick-up head in the prior art plate feeders, this gap must be created by holding the stack back from the pick-up unit or by pushing the stack away from the pick-up unit immediately before a pick-up unit comes into alignment with the stack.
In Johnson, et al., U.S. Pat. No. 4,462,745, this gap is created by placing the pick-up units on chordal segments of the pick-up head thereby placing them radially inwardly of the periphery of the pick-up head. The periphery of the pick-up head then holds the stack away from the pick-up unit until a pick-up unit arrives. In Johnson, et al., U.S. Pat. No. 4,758,126, push-back rollers are placed at the periphery of the pick-up head in front of each pick-up unit and the rollers push the stack of plates back from the periphery of the pick-up head as a pick-up unit approaches. Because of this need to hold the plates back or push the plates back to create a gap between the pick-up unit and the stack or plates, the gap is not consistent in the prior art feeders. In addition, a plate being picked up by a pick-up unit can only be successfully gripped if the amount the plate is accelerated when it is picked up is kept below a certain level. In order to stay below this level of acceleration, the surface speed of the plates should not exceed approximately 100 feet per minute. Finally, because the plates have to be separated from one another as they are conveyed away from the device for further processing, the plates have heretofore been separated from one another on the pick-up head also. As a result, the prior art plate feeders have been limited to the number of pick-up units that will not result in overlapping of the plates. This need to maintain plate separation on the pick-up head and not to exceed a certain pick-up unit surface speed at pick up has placed a limit on the rate at which plates can be fed on this type of machine.
The need exists, therefore, to feed plates cleanly at a higher rate than is possible with these prior art devices.
While plate feed apparatus have in the past fed plates from vertical stacks that are lifted toward the pick-up head each time a plate is removed from the stack, vertical stack feed mechanisms have not heretofore had enough precision to be used in conjunction with rotating cylindrical pick-up heads having multiple pick-up units through which a vacuum is drawn to feed battery plates.
A first aspect at the subject invention overcomes the difficulty prior art battery plate feeders have in creating a uniform gap between the plates and the pick-up unit prior to picking up a plate and allows the pick-up head to be rotated at a higher speed. A cylindrical pick-up head has a predetermined number of pick-up units placed about its periphery. The pick-up head is attached to a first shaft which is coaxial with the centerline of the pick-up head and the pick-up head and the first shaft are rotated at a first rotational speed. A feed mechanism places the outermost plate in a stack of plates a nominal distance from the periphery of the pick-up head each time a plate is removed from the stack. A vacuum device is selectively coupled to each pick-up unit as it is rotated over the stack to draw a vacuum through the pick-up unit and pull the outermost plate away from the stack and into contact with the pickup unit.
A second shaft has a cylindrical bore which rotatably journals the first shaft. The bore on the second shaft is offset from the centerline of the second shaft so that the first and second shafts are not coaxial. The second shaft is rotated counter to the rotation of the first shaft and at a rotational speed that is a multiple of the rotational speed of the first shaft equal to the number of pick-up units. The rotation of the first and second shafts are coordinated such that this counter rotation and axial misalignment causes the surface speed of each pick-up unit to slow down as it rotates into position to pick-up a plate from the stack and causes each pick-up unit to move closer to the stack of plates as it rotates into position to pick-up a plate from the stack. Because the pick-up unit slows down at the pick-up point, the pick-up head can be rotated at a higher rotational speed than would heretofore be possible with a pick-up head having the same diameter, and still not exceed the critical surface speed at pick-up. Thus, higher plate feed rates are possible. Furthermore, since the pick-up head moves closer to the stack when a plate is picked up and then moves further away from the stack, the plates are less likely to strike the stack as they are rotated away from it.
Another aspect the subject invention overcomes the inability at the prior art battery plate feeders to operate above a maximum feed rate without over accelerating the plates upon pick-up, or having the plates overlap one another as they are removed from the feed head. The pick-up head is provided with additional pick-up units, and the plates overlap one another on the pick-up head. The outfeed conveyer, which carries the plates out of the device, has a surface speed which is higher than the surface speed of the pick-up units so that the plates do not overlap one another on the outfeed conveyer. Thus, the acceleration of the plates is divided between pick-up and placement on the outfeed conveyer, and the feed rate can be greatly increased.
A third aspect of the invention overcomes the lack of precision in the prior art vertical feed mechanisms and provides a uniform gap between the pick-up head and the stack of plates. The platform that supports the stacks of plates is raised and lowered by a lifting mechanism. A first sensing device senses when the uppermost plate in the stack is the proper distance from the pick-up head. When a plate is removed from the stack, the first sensing device signals a controller and the controller causes the platform to be raised until the next plate in the stack is sensed by the first sensing device. A second sensing device senses when the platform reaches a predetermined level, which is below the level of the first sensing device. A support frame has a set of fingers which can be inserted under the platform below the stack of plates. An activation mechanism moves the fingers between an extended position under the plates and a retracted position free from the plates. A second lifting mechanism raises and lowers the support frame. When the second sensing device senses the platform is at the predetermined height, it signals the controller and the controller causes the fingers to be inserted under the platform and causes the second lifting mechanism to raise until the fingers engage the stack of plates. The second lifting mechanism then lifts the stack of plates each time a plate is removed from the stack, and the platform is lowered to receive a second stack of plates. When a new stack of plates has been placed on the platform it is raised again until the top of the second stack of plates contacts the bottom of the first stack of plates and the platform then moves the two stacks of plates to maintain the uppermost plate at the proper location and the fingers are moved to their retracted position.
The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.